Machines such as, for example, passenger vehicles, trains, marine vessels, construction equipment, excavating machines, etc., often have a combustion engine to power various operations of the machine. In the past, the power output of the combustion engine was usually mechanically coupled to traction devices (e.g., wheels or tracks) to propel the machine. In response to ever more stringent emissions requirements and design goals, however, different propulsion arrangements have been developed. Combustion engines are now commonly used to drive an electric machine, such as an inductance machine, a permanent magnet machine, or switched reluctance machine, which operates in a generating mode to energize a DC bus that is used to power an electric motor at the traction devices. This arrangement is advantageous because it permits running the combustion engine at a constant speed (i.e., a “sweet spot”) that minimizes harmful emissions and/or maximizes fuel economy.
During operation of such machines, an undesirable situation arises when the insulation of an energized winding fails and the electrical source is shorted to the housing of the generator or motor and/or the chassis of the machine. For example, damage to the machine or systems thereof may result. As such, there is a need to detect winding faults and take precautions in response thereto.
One winding fault detection circuit is described in U.S. Pat. No. 5,574,346 issued to Chavan et al. on Nov. 12, 1996 (the '346 patent). The winding fault detection circuit monitors voltage drops in the phase windings of a motor and compares the voltage drops with reference voltages to determine if the motor is out of normal operating range parameters and if a valid fault exists. If a valid fault exists, a circuit driving the motor is interrupted.
Although the fault detection circuit of the '346 patent may interrupt operation when a winding fault is detected, it may be overly complex, costly, and difficult to implement. For example, the fault detection circuit requires comparator logic to monitor the windings of each phase of the motor and to compare the voltage drops across each winding to a high reference voltage and a low reference voltage. In addition, the outputs of the comparator logic must be sequentially selected and provided to fault logic in accordance with the excitation of respective phase windings and the angular position of the motor. Only at this point may analysis be made as to whether a winding fault is present.
The present disclosure is directed to overcoming one or more of the problems set forth above.